Method for the selective alpha halogenation of alkylaromatic compounds

ABSTRACT

Inorganic and organic hypohalites are used to obtain good selectivity to alpha halogenation of alkyl aromatic compounds. Alkali and alkaline earth hypohalites must be used in conjunction with a phase transfer medium. Useful organic hypohalites are the tertiary alkyl hypohalites, which are employed in the presence of free radical generating media such as light or compounds which produce free radicals thermally. At least one mole of hypohalite reactant must be used for every alpha hydrogen in the alkyl aromatic compound. 
     A new bisphenol which contains biphenyl functionality has been made as well as an aromatic polyester derived therefrom.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 07/472,507, filed 1-29-90,now U.S. Pat. No. 4,992,15

BACKGROUND OF THE INVENTION

During the past fifty years the side chain chlorination of ethylbenzenehas been studied with a number of different chlorinating agentsincluding hypochlorites. Very good selectivity to alpha chlorination wasobserved, but only to monochlorination There are no examples of apreparative method for the selective halogenation of alkylaromatics tocompounds having at least two alpha halogen substituents, especiallywhen beta hydrogens are present on the side chain.

Various references over the years have disclosed the chlorination ofethylbenzene using different chlorinating agents. The predominantproduct is α-chlorethylbenzene with some β-chlorethylbenzene orα,β-dichlorethylbenzene, but little or no α,α-dichloroethylbenzene.Representative references are J.Am.Chem. Soc. 61, 2142 (1939);Chem.Abst. 41:3437a (1947); Bull. soc.chim.Belges 59, 193(1950):J.Org.Chem. 28, 3173 (1963); J.Org.Chem. 39, 3472(1974) and J.Org.Chem.44,2270(1979).

The chlorination of diethylbenzene in the presence of PCl₅ and lightshowed poor selectivity to multichlorination in the alpha positions[Macromol. 6, 815(1973)]. Analysis of the product of the reaction ofmeta-diethylbenzene with chlorine and PCl₅ conducted at 90°-100° C. witha 300 w incandescent light lamp showed a reaction mixture containing "atleast 25 different components of which 6-8 could be considered majorconstituents".

British patent 1,563,164 (1980) describes the preparation ofα,α-dichloroethylaromatic compounds by a chlorination with molecularchlorine of the corresponding monochlorinated ethylaromatic compoundsusing a phosphorus halide catalyst, e.g. PCl₃ or PCl₅, in the presenceof light or other initiator. Selectivities of 80-90% to the desiredα,α-dichloroethylaromatic compounds are taught, but conversion of theethylaromatic is only up to about 50%. A comparative example in whichthe same system was used starting with ethylbenzene gave a productmixture of 58.5% α-chloroethylbenzene, 31.5% α,α-dichloroethylbenzene,6.8% α,β-dichloroethylbenzene and 3.2% higher chlorinated products.

In 1945 Prof. J. Kenner reported [Nature 156, 369(1945)] that hiscolleague Dr. R. F. Garwood had demonstrated that t-butyl hypochloritein the presence of benzoylperoxide effectively chlorinated ethylbenzeneto α-chloroethylbenzene. No experimental conditions, yields or theformation of any dichloro- products were mentioned.

In 1960 Walling initiated a series of studies on t-butyl hypochlorite asa chlorinating agent [J.A.C.S. 82, 6108(1960)]. These focused onkinetics and mechanism, and the reaction conditions involved largeexcesses of hydrocarbon over tert-butyl hypochlor-ite. In the case ofthe chlorination of alkylaromatics, little or no dichlorination wasobserved, and there is no mention of the selectivity to dichlorination.

U.S. Pat. No. 3,251,887 (1966) employs trichloromethanesulfonyl chloridein the presence of a free-radical generating catalyst to chlorinateethylbenzene selectively to obtain (1-chlorethyl)benzene and states thatin the case of ethylbenzene, tert-butyl hypochlorite gives no betterselectivity to the alpha over the beta isomer in monochlorination thandoes the photochlorination with molecular chlorine.

Sodium hypochlorite (bleach) at a pH of 7.5-9 in the presence of phasetransfer catalysts selectively chlorinates alkylaromatics in the alphaposition [J.A.C.S. 105, 7672, (1983)]. For a 94% toluene conversion theproduct yields were: benzyl chloride (64%), benzal chloride (11%), withcompounds such as benzoic acid, cresols, benzaldehyde, benzyl alcoholand ring chlorinated compounds making up the remainder. No attempt wasmade to optimize dichlorination and for the ethylbenzene reaction noproduct distribution was given.

SUMMARY OF THE INVENTION

Hypohalites are reacted with alkylaromatics having at least twoalpha-hydrogens and at least one beta-hydrogen on each alkyl moiety toobtain halogenated alkylaromatic compounds containing at least twoalpha-halogens with little or no beta-halogenated co-products.

Both inorganic and organic hypohalites can be used to obtain goodselectivity to di-alpha halogenation. Alkali and alkaline earthhypohalites must be used in a phase transfer medium. Effective organichypohalites are the tertiary alkyl hypohalites in the presence of a freeradical generating medium, e.g. light, free radical generating catalystsor compounds which will thermally produce free radicals. At least onemole of hypohalite reactant must be used for every alpha hydrogen in thealkyl aromatic compound.

DETAILED DESCRIPTION OF THE INVENTION

The alkylaromatic compounds useful in the process of the invention arethose which contain at least two alpha hydrogens, i.e., hydrogen atomsbonded to carbon atoms which are in turn bonded directly to an aromaticring, and at least one beta hydrogen on each alkyl moiety, i.e. ahydrogen bonded to a carbon atom attached to an alpha-carbon on thealiphatic side-chain. Representative mono-substituted alkylaromaticcompounds, wherein the alkyl side chain may contain 2 to 12 carbonatoms, are alkylbenzenes, alkylnaphthalenes, alkylanthracenes,alkylbiphenyls and the like compounds which possess at least two alphahydrogens and at least one beta-hydrogen on each aliphatic side chain.Representative of this type of compound are ethylbenzene,n-propylbenzene, n-butylbenzene, n-octylbenzene, n-decylbenzene,n-dodecylbenzene ethylphenyl acetate, ethylnaphthalene, diethylbenzene,diethylnaphthalene, ethylanthracene, ethylbiphenyl, diethylbiphenyl,n-propylbiphenyl, ethylthiophene, phenethyl alcohol, indane, 1-indanone,indene, dihydro-coumarin, 2-ethylanthraquinone, 4-ethylacetophenone,4-ethylphenol and the like. Also representative are di-, tri- and morehighly substituted alkyl aromatics containing one alpha hydrogen and atleast one beta-hydrogen per alkyl group such as diisopropyl benzene,diisopropyl biphenyl, diisopropyl naphthalene, triiso-propylbenzene andthe like.

Other compounds which are precursors of the dialphahaloalkylaromaticcompounds made by the process of the present invention arealkyl-substituted furans, thiophenes, pyridines, pyrazines, pyrroles andthe like.

In one aspect of the invention an aromatic compound, having at least twoalpha-hydrogens, and at least one beta-hydrogen on each alkyl moiety, iscontacted with a halogenating agent which will preferentially substituteeach alpha-hydrogen.

While chlorinating agents such as chlorine, phosphorous pentachlorideand sulfuryl chloride are capable of chlorinating the α-carbon of thealkyl substituent, attempts at polychlorination cause numerous otherchlorinated derivatives to be formed. Hypochlorites, when used as themeans for the chlorination, are more selective and will cause thechlorines to substitute the α-hydrogens preferentially. Thus, forexample, in the chlorination of ethylbenzene with t-butyl hypochloriteaccording to the present invention, the ratio of α,α-dichlorethylbenzeneto other multichlorinated species is 90-100/1. This is illustrated inExamples 1, 3, 4, 5 and 6.

While an alkali metal hypohalite can be used in conjunction with a phasetransfer catalyst, the preferred halogenating agent is a t-alkylhypohalite such as t-butyl hypochlorite. In either method the amount ofhypohalite must be at least two moles for each mole of the alkylaromaticcompound. In the preferred method the alkyl-substituted aromaticcompound and t-alkyl hypohalite are contacted in the presence of afree-radical generating medium, optionally in a solvent. The preferredtertiary alkyl hypohalites are t-butyl hypochlorite or t-amylhypochlorite, the former being most preferred. For other t-alkylhypochlorites see the table in Greene et al. J. Org. Chem. 28 55,(1963). The temperature of the reaction should be controlled so asprevent the thermal decomposition of the hypohalite. The by-productalcohol is subsequently removed by distillation along with any solventpresent, leaving the desired dialphahaloalkylaromatic compound.

The following equation, showing the dialphachlorination of ethylbenzene,is representative of the invention: ##STR1##

The temperature employed in the reaction is controlled at from about-70° C. to about 80° C., preferably at about 0° to 25° C. Thet-alkylhypohalites will decompose at elevated temperatures, e.g. t-butylhypochlorite will decompose explosively at temperatures in excess of 80°C.

The temperature is conveniently controlled by controlling the amount oflight incident on the reaction mixture and by external cooling of thereactor. If the light source is removed the reaction ceases immediately.The reaction can also be stopped by the addition of air or oxygen to thereaction medium. The time of reaction is dependent upon the temperatureand the light flux, but is generally complete within 2-3 hours.

Free radical catalysts useful in the invention are, for example,peroxides such as t-butyl peroxide and t-amyl peroxide andhydroperoxides such as chloro-t-butyl hydroperoxide, cumenehydroperoxide and cyclohexane hydroperoxide.

Compounds which produce free-radicals thermally which are useful in theinvention are diazo compounds such as azobisisobutyronitrile and diacylperoxides such as isobutyroyl peroxide.

Solvents useful for the reaction are aromatic hydrocarbons having from 6to 12 carbon atoms. The halogenated derivatives of aliphatic andaromatic hydrocarbons, especially the chlorinated derivatives, are alsouseful. The hypohalites themselves can serve as solvents for thereaction.

The ratio of reactants employed is at least two moles of the alkalimetal or t-alkyl hypohalite for each mole of the alkylaromatichydrocarbon. Operable limits are from about 2 to about 2000 moles of thehypohalite per mole of alkylaromatic compound; the preferred range ofhypohalite being from about 2 to about 10 moles per mole ofalkylaromatic compound

The di-, tri-, tetra- and higher alphahaloalkyl products of thehalogenation reaction are useful in the preparation of the correspondingdi-, tri- tetra- and higher phenols by reacting these halogenationproducts with a phenol. These polyphenols are valuable precursors tohigh performance engineering thermoplastics such as polycarbonates andpolyarylates, or in high performance cross-linked polymers such as epoxyresins. Alternatively the alphahaloalkyl products of the invention canbe dehydrohalogenated to form alkynylaromatic compounds. The di- andtriethynyl aromatic compounds are valuable precursors to thermosettingpolyphenylenes. Some such products are available commercially as"H-Resins" from Hercules Inc.

The following examples are representative of the invention:

EXAMPLE 1 Preparation of 1,1-dichloroethylbenzene by Phase TransferChlorination of Ethylbenzene

A solution of sodium hypochlorite (1000 mL of bleach, 5.25% NaOCl, 52.5g, 0.70 mole) is placed into a 2-liter, 5-neck flask equipped withthermometer, pH probe and a mechanical stirrer The pH is adjusted from12.5 to 8.0 with conc. HCl. Methylene chloride (250 mL, 331 g, 2.22moles) is added, followed by tetrabutylammonium bromide (6.45 g, 0.02mole) and t-butyl alcohol (0.76.mL, 0.6 g, 0.008 mole). Ethylbenzene(12.23 mL, 10.6 g, 0.10 mole) is added at once and the mixture isstirred vigorously. The pH of the solution drops to 7.10 as thetemperature rises from an initial 25° C. to 38° C. in 30 minutes. Gaschromatography (GC) analysis at this point shows no ethylbenzeneremaining. The product mixture contains 1,1-dichloroethylbenzene (78%),1-chlorostyrene (7%), 1-chloroethylbenzene (3%), 2-chloroethylbenzene(2%) and acetophenone (10%).

EXAMPLE 2 Preparation of 1,1,1',1'-tetrachloroethylbenzene fromDiethylbenzene Using an Alkali Metal Hypochlorite and a Phase TransferCatalyst

In the manner of Example 1, aqueous NaOCl (1000 mL, 55 g, 0.72 mole) isplaced in an identical flask equipped in the same fashion. The pH of thesolution is adjusted as before to 8.0 and 250 mL of CH₂ Cl₂ is added,followed by 6.71 g (0.05 mole) of diethylbenzene and 6.45 g (0.02 mole)of tetra-n-butylammonium bromide. After 30 min. of stirring, thetemperature of the mixture rises from 25° C. to 37.8° C., and the pH to8.45. At this time G.C. analysis shows no remaining diethylbenzene andonly a single product. The stirring is stopped and the phases areallowed to separate. The organic phase is dried with MgSO₄, filtered andthe solvent is removed on a rotary evaporator to give a pale yellowresidual oil (13.52 g, 99% theoretical) which is shown by NMR analysisto be the desired 1,1,1',1'-tetrachloroethylbenzene.

The following examples are conducted according to the most preferredmethod, i.e. employing t-butyl hypochlorite as the chlorinating agent.

EXAMPLE 3 Preparation of 1,1-dichloroethylbenzene Using t-butylhypochlorite.

Into a 5-neck 2-liter flask, equipped with thermometer, mechanicalstirrer and a pH probe, is placed 1000 mL of an aqueous bleach solution(˜5.25% NaOCl). The flask is placed in an ice bath and cooled to 8° C.and t-butyl alcohol (56.5 mL, 0.59 mole) and glacial acetic acid (34.35mL) are added with stirring. The temperature rises to about 15° C. andthe pH drops from about 11.3 to about 6.5. Stirring is continued forabout five minutes and then allowed to phase-separate, during which timea yellow oil floats to the surface. Ethylbenzene (36.9 mL, 0.30 mole) isadded, stirring resumed and a 275-watt sun lamp is placed over theflask. The mixture is stirred with illumination for one hour while thetemperature is maintained within the range of 8°-18° C., after whichstirring is stopped and the mixture is allowed to phase-separate.

The aqueous phase is extracted with two×100 mL portions of methylenechloride and combined with the organic phase. The combined solvent andorganic phase is then dried over MgSO₄ and the solvent is removed bydistillation, leaving 52.01 g of oil. G.C. analysis shows that theproduct is 73.6% 1,1-dichloroethylbenzene, 10.34% 1-chloroethylbenzeneand 10.48% acetophenone and some minor impurities.

The following three experiments (Examples 4, 5 and 6) show the use ofother solvents in the reaction using t-butyl hypochlorite as thechlorinating agent.

EXAMPLE 4 Use of Carbon tetrachloride as Solvent

A quantity of t-butyl hypochlorite (7.0 mols, 759.99 g, 775 mL) ischilled to -5° C. in a brine jacketed reaction flask equipped withmechanical stirrer, light well, thermometer and nitrogen supply.Ethylbenzene (2.0 mole, 213.4 g, 246 mL) in CCl₄ (10.4 moles, 1594 g,1000 mL) is added to the reactor and the reaction is started by turningon the lamp (incandescent, 25 watt lamp, General Electric modelFG648-X). The reaction temperature is allowed to rise to 10° C. andsamples are taken periodically for G.C. analysis. After 4 hours thereaction is complete and the mixture is drained from the reactor and thet-butanol is stripped using a rotary evaporator which leaves 322.62 g ofa colorless oil which is 89.4% 1,1-dichloroethylbenzene by G.C. analysis(82.3% yield).

EXAMPLE 5 Use of Benzene as Solvent

The reaction of Example 4 is repeated except that benzene (11.18 moles,874 g, 1000 mL) is used in place of carbon tetrachloride. The t-butanolis removed on a rotary evaporator and there remains 341 g of a colorlessoil which is 91.7% 1,1-dichloroethylbenzene by G.C. analysis (89.3%yield).

EXAMPLE 6 Use of t-butyl hypochlorite as Solvent

Ethylbenzene (4.0 mole, 424.68 g, 492 mL) is charged to a brine jacketedreaction flask equipped with a subsurface N₂ sparge, light well,thermometer and condenser. The t-butyl hypochlorite (14.0 mole, 1520 g,1670 mL) is added to the reactor and the mixture is chilled to -5° C.while sparging with N₂. The same lamp employed in Example 4 is switchedon to initiate the reaction which is conveniently held at 0° C. bycontrolling the lamps' output with a temperature controller. Samples aretaken periodically and analyzed by G.C. analysis. When the reaction iscomplete (3 hours) the mixture is drained from the reactor and thet-butanol and excess t-butylhypochlorite is removed on a rotaryevaporator, leaving 709.0 g of a clear oil which is 93.2%1,1-dichloroethylbenzene by G.C. (93% yield).

EXAMPLE 7 Preparation of 4(1,1-dichloroethyl)biphenyl

A quantity of 4-ethylbiphenyl (0.41 mole, 75 g) is charged to thereactor described in Example 6 in CCl4 (3.10 moles, 478.2 g, 300 mL)followed by t-butylhypochlorite (1.20 moles, 134.0 g, 147 mL). Thereaction is carried out as in Example 6 and the usual work-up, using therotary evaporator, gives 98.7 g (95.8% yield) of white crystals of4-(1,1'-dichloroethyl)biphenyl.

EXAMPLE 8 Preparation of bis-1,4(1,1-dichloroethyl)benzene

The 1,4-diethylbenzene (2.0 mole, 268.44 g, 310 mL) is charged to thereactor followed by t-butylhypochlorite (12.0 moles, 1302.84 g, 1500mL). The reaction is carried out as in Example 6 and after the usualwork-up (as in the preceding examples) there is obtained 542.34 g(99.6%) of glistening white crystals ofbis-1,4-(1,1-dichloroethyl)benzene.

EXAMPLE 9 Preparation of 4-(1,1-dichloroethyl)phenylacetate

Quantities of 4-ethylphenylacetate (4.0 mol, 656.8 g) andt-butylhypochlorite (12.0 mole, 1302.8 g, 1431 mL) are charged to thereactor and chilled to -5° C. The reaction is carried out as in Example4. After the usual work-up there is obtained 857.79 g (92%) of a paleyellow oil, the 4-(1,1-dichloroethyl)phenylacetate.

EXAMPLE 10 Preparation of 1,3,5-tris(1-chloro-1-methylethyl)benzene

A 500-mL flask equipped with stirring means and a nitrogen sparge ischarged with triisopropylbenzene (TIPB, 20 g, 98 mmole) and stockt-BuOCl (2.2 moles in CCl₄) solution (270 mL, 590 mmole) and chilled inan ice-water bath. With stirring and nitrogen sparge, the mixture isirradiated with a 250-watt sunlamp. The temperature is kept between 10°and 25° C. by shutting off the lamp as the temperature approaches 25°and turning it back on as the temperature approaches 10° C. The reactionis continued until the solution is colorless (2 hrs). CCl₄ andby-product t-butanol are removed in vacuo to give 35.7 g of a cloudyoil. Pentane (30 mL) is added and the solution is chilled to -15°,giving 1,3,5-tris(1-chloro-1-methyl-ethyl)benzene as white crystals(15.8 g, 51 mmole, 52% yield), m.p. 64° (lit.69°).

EXAMPLE 11 Preparation of 4,4'-bis(1-chloro-1-methylethyl)biphenyl

A one-liter flask, equipped with stirring and nitrogen-sparging means,is charged with 4,4'-diisopropylbiphenyl (DIPBP, 85 g, 0.36 mol) and asolution of t-BuOCl (500mL, 1.1 mols), from the same stock solutionemployed in Example 10 above, and the mixture is chilled in an ice-waterbath. While stirring and sparging with nitrogen, the contents areirradiated with the same type lamp used in Example 10. The temperatureis maintained between 10° and 25° C. by shutting off the power when thetemperature of the reaction reaches 10° C. The reaction is continueduntil the solution becomes colorless (ca. 2 hrs), indicating that allthe t-BuOCl has been consumed. The solvent CCl₄ and by-product t-butylalcohol are removed under vacuum to give 111.5 g of4,4'-bis(1-chloro-1-methylethyl)biphenyl (DIPBP-Cl₂). The DIPBP-Cl₂ iscrystallized from hexane to give white crystals, m.p. 96°-98° C. This isa new compound not disclosed in the literature.

EXAMPLE 12 Preparation of4,4'-bis[1-(4-hydroxyphenyl)-1-methylethyl-biphenyl

A one-liter flask, equipped with stirring means and a gas take-off tubeconnected to a water bubbler, is charged with DIPBP-Cl₂ (110 g, 0.36mol) and phenol (340 g, 3.6 mols). The mixture is heated to 115° C.while stirring, using the water bubbler to maintain a slight positivepressure of HCl (a by-product of the reaction) in the flask. After 1.5hrs, the mixture is cooled and excess phenol and HCl are removed undervacuum. The product is purified to remove residual phenol by dissolvingin a minimum of boiling methanol (ca. 100 mL), adding 500 mL water andboiling with vigorous stirring for about 2 hrs. While continuing thestirring, the mixture is allowed to cool to room temperature andfiltered. The solid product is dried under vacuum. The resulting tanpowder is dissolved in boiling CHCl₃ and crystallized therefrom, giving101.7 g of light beige crystals of4,4'-bis[1-(4-hydroxyphenyl)-1-methylethyl]biphenyl (BP-DIPBP), m.p.195°-6° C. The yield is 67% of theoretical. This is a new bisphenol notpreviously known to the art.

The method of making aromatic polyesters from bisphenols is well knownand conditions for the reaction include: (1) temperatures within theliquid ranges, e.g. from about -70° to about 300° C., preferably fromabout 0° to about 50° C.; (2) solvents for the reaction, such asaliphatic and aromatic hydrocarbons and their halogenated derivatives,e.g. xylene, toluene, sulfolane, dichloroethane, chloroform, methylchloroform, chlorobenzenes and the like; (3) reactants preferablyemployed in the solvent at concentrations of from about one to about 50percent by weight based on the total reaction mixture; and (4) ratios ofbisphenol to terephthalic and/or isophthalic acid or their acidchlorides of from about 0.9 to about 1.1 moles of bisphenol per mole ofacid or acid chloride.

The following example illustrates the use of the bisphenol of Example 12in making a polyester:

EXAMPLE 13 Preparation of an Aromatic Polyester From BP-DIPBP.

A 1-qt blender is charged with BP-DIPBP (21.1 g, 0.0500 mole); NaOH(4.00 g, 0.100 mole); water (330 mL); and benzyltriethylammoniumchloride (BTEAC, 1.5 g, 0.0065 mole). The mixture is stirred at lowspeed at room temperature for 10 min. A solution of isophthaloylchloride (IPC) and terephthaloyl chloride (TPC) (5.08 g each, 0.0250mole each) in CHCl₃ (150 mL) is added quickly and the mixture is blendedat high speed for 10 min. The phases are separated in a separatoryfunnel; and the organic (heavier) phase is poured into rapidly stirringacetone (300 mL). The resulting polymer precipitate is washed with water(300 mL) and then acetone (300 mL) and then dried in a vacuum oven (100°C.) overnight. The resulting pale yellow powder has a glass transitiontemperature (Tg) of 237° C. and a weight-averaged molecular weight of39,400 (relative to polystyrene standards).

A polyarylate, made under the same conditions for comparison by reactingthe same ratios of phthaloyl chlorides with Bisphenol A, gives a whitepowder which has a Tg of 212° C. and a weight-averaged molecular weightof 31,900 (relative to polystyrene standards).

We claim:
 1. A process for producing an aliphatic substituted aromaticcompound having a least two alpha- halogen substituents which comprisescontacting a reactive hypohalite compound with an aromatic compound,having at least one aliphatic substituent, and which contains at leasttwo alpha-hydrogens, and in which each aliphatic substituent contains atleast one beta-hydrogen in the presence of a free radical generatingmedium wherein the hypohalite compound is an alkali or an alkaline earthmetal hypohalite and wherein the reaction is conducted in the presenceof a phase-transfer medium.
 2. The process of claim 1 wherein the alkalior an alkaline earth metal hypohalite is a hypochlorite.
 3. The processof claim 2 wherein the alkali metal hypochlorite is sodium or potassiumhypochlorite.
 4. The process of claim 2 wherein the alkaline earthmetalhypochlorite is calcium or magnesium hypochlorite.
 5. The processof claim 1 wherein the phase-transfer medium is a quaternary ammoniumsalt.
 6. The process of claim 5 wherein the quaternary ammonium salt isa tetraalkylammonium halide.
 7. The process of claim 6 wherein thetetraalkylammonium halide is tetrabutylammonium bromide.
 8. The processof claim 7 wherein the reaction is controlled at a temperature of fromabout -70° C. to about 80° C.
 9. The compound4,4'-bis(1-chloro-1-methylethyl)biphenyl.
 10. The compound4,4'-bis[1-(4-hydroxy-phenyl)-1-methylethyl]-biphenyl.
 11. An aromaticpolyester containing biphenyl functionality derived from4,4'-bis[1-(4-hydroxyphenyl)-1-methylethyl]-biphenyl.